Antiviral carbocyclic analogs of xylofuranosylpurines

ABSTRACT

Biologically-active (6-amino) purine nucleosides of the formula: ##STR1## are disclosed wherein X is CH or N, and R is selected from the group consisting of N(Y)(Z), SY, OY and halogen, wherein Y and Z are H, lower(alkyl), phenyl or mixtures thereof; and the pharmaceutically-acceptable salts thereof. The compounds exhibit antiviral and antitumor activity.

This invention was made with Government support under Grant Number 2R01CA23263, awarded by the National Institute of Health. The Government hascertain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to carbocyclic analogs of purinenucleosides which exhibit antiviral and cytotoxic activity.

BACKGROUND OF THE INVENTION

Despite intensive efforts to discover drugs that may be of value in thesystemic treatment of virus infections, such infections have beensingularly resistant to chemotherapy. The intracellular and intimaterelation to nuclear metabolism of virus reproduction makes it difficultto destroy a virus without irreparable damage to the host cell.

The discovery of the antiviral activity of vidarabine(9-β-D-arabinofuranosyladenine monohydrate) has led to the preparationof a large number of synthetic nucleosides. For example, the synthesisof adenine ("6-amino-purine") nucleoside analogs in which the pentosesugar has been replaced with a hydroxy-substituted cyclopentyl residuehas yielded compounds with substantial cytotoxic and antiviral activity.However, the structure-activity relationships between thevariously-substituted 9-(cyclopentyl)adenines which have been preparedand tested remain ill-defined.

For example, H. Lee and R. Vince, in J. Pharm. Sci., 69, 1019 (1980)disclosed the 2-amino-6-substituted purines of formula I (R=NH₂ or OH,X=CH or N). ##STR2##

In these compounds, the arabinofuranosyl residue has been replaced witha 1α,2β-dihydroxy-5α-hydroxymethylcyclopent-3α-yl moiety where thedesignations "α" and "β" refer to substituents which are respectively,above and below the plane of the cyclopentane ring as it is depicted informula I. The compound of formula I where R=NH₂ and X=CH exhibitedactivity against Herpes simplex virus, type 1 (HSV-1), but was inactiveagainst HSV-2. The other compounds of formula I exhibited no significantantiviral activity.

R. Vince et al., in J. Med. Chem., 27, 1358 (1984) disclosed thecarbocyclic xylofuronosyl adenine and 8-aza-adenine compounds of formulaII (X=CH or N). ##STR3##

The removal of the 2-amino group present in the compounds of formula I(R=NH₂) and the inversion of the stereochemistry of the 1,2-dihydroxysubstituents on the cyclopentyl ring to yield the compounds of formulaII resulted in the loss of antiviral activity. However, compounds offormula II (X=CH) substituted with the cyclopentyl moiety shown informula I have been disclosed to exhibit substantial activity againstHSV-1 and HSV-2. See, R. Vince and S. Daluge, in J. Med. Chem., 20, 612(1972).

Thus, a substantial need exists for chemotherapeutic agents effective toprotect mammalian cells against infection by viruses such as HSV-1,HSV-2, AIDS, varicellazoster, vaccinia, cytomegalovirus and the like.

SUMMARY OF THE INVENTION

The present invention is directed to carbocyclicxylofuranosyl-substituted (2-amino)purines of the formula: ##STR4##wherein X is CH or N and R is selected from the group consisting ofN(Y)(Z), SY, OY and halogen, wherein Y and Z are H, lower(C₁ -C₄)alkyl,phenyl or mixtures thereof, and the pharmaceutically acceptable saltsthereof. Preferably R is Cl, OH or NH₂. These compounds are effectiveantiviral and/or cytotoxic agents or are intermediates useful for thepreparation thereof. It is believed that the antiviral activity is dueto an inhibitory effect on the ability of viruses to infect normalmammalian cells, and to their resistance to in vivo deamination byadenosine deaminase. The present invention is also directed to theintermediate compound of the formula: ##STR5## wherein Z is halogen,preferably Cl, which is useful for the preparation of the(2-amino)purines of the invention. Thus, it is expected that thecompounds of the present invention will be useful against viralinfections or virus-associated tumors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are flow diagrams summarizing the synthesis of the(2-amino)purines of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The synthesis of the carbocvclic xylofuranosylaine, (d1)-(1 α,2 β,3 α,5α)-3-amino-5-(hydroxymethyl)-1,2-cyclopentanediol (2), from theversatile precursor, 2-azabicyclo[2.2.1]hept-5-ene-3-one (1), wasaccomplished as described by R. Vince et al. in J. Med. Chem., 27, 1358(1984), the disclosure of which is incorporated bv reference herein. Asshown in FIG. 1, condensation of 2 with2-amino-4,6-dichloropyrimidine(3) gave the correspondingpyrimidinylamino derivative (4) along with disubstituted product 5. Theassignment of structure 5 is consistent with its infrared, NMR, andspectral analyses. Also, the presence of two NH signals at δ9.82 andδ7.80-7.72 and one NH₂ signal at δ6.67 in the NMR spectrum rules out thepossibility that both pyrimidine moieties were attacked by the 3-aminogroup of 2.

The 5-(p-chlorophenylazo) pyrimidine (6) was prepared withp-chlorobenzenediazonium chloride by the method of Shealy and Clayton,in J. Pharm. Sci., 62, 1432 (1973). Reduction of 6 with zinc and aceticacid gave the pyrimidine 7, which was subsequently converted to the9-substituted 2-amino-6-chloropurine (8) by ring closure with triethylorthoformate and subsequent mild acid hydrolysis to removeethoxymethylidenes and formates formed during the reaction.

Treatment of 8 with 1N hydrochloric acid under reflex conditions gavecarbocyclic xylofuranosylguanine (9a), while treatment of 8 with liquidammonia yielded the carbocyclic xylofuranosyl 2,6-diaminopurine (10a).

Treatment of 8 with thiourea in refluxing alcohol, followed by alkalinehydrolysis affords thiol 9b. See L. F. Fieser et al., Reagents forOrganic Synthesis, John Wiley and Sons, Inc., N.Y. (1967) at pages1165-1167 and U.S. Pat. No. 4,383,114, the disclosures of which areincorporated by reference herein. Phenyl or alkylthio-derivatives (9c,R'=phenyl or (lower)alkyl) can be prepared from the corresponding thiol9b by the procedure of U.S. Pat. No. 4,383,114 (Example 6).

Mono- or disubstituted 6-amino compounds of formula 10b(R"=R"'=(lower)alkyl, phenyl or mixtures thereof with H can be preparedby conventional methods for the conversion of halides to secondary ortertiary amines. For example, see I. T. Harrison, et al., Compendium ofOrganic Synthetic Methods, Wiley-Interscience, N.Y. (1971) at pages250-252. The 6-chloro substituent in compounds 6-8 can be replaced withother halogen atoms by the use of various p-(halo)benzene diazoniumchlorides in the conversion of 4 to 6, or by conventional methods ofhalide-halide exchange.

These conversions are extensively described in the context of purinenucleoside synthesis in Nucleoside Analogs-Chemistry, Biology andMedical Applications, R. T. Walker et al., eds., Plenum Press, N.Y.(1979) at pages 193-223, the disclosure of which is incorporated byreference herein.

The 8-azapurine analogs were obtained as outlined in FIG. 2. Ringclosure 7 with sodium nitrite and acetic acid gave (1 α,2 β,3 α,5β)-(d1)-3-(5-amino-7-chloro-3H-1,2,3-triazolo[4,5-d]pyrimidin-3-yl)-5-(hydroxymethyl)-1,2-cyclopentanediol(11) in good yield. When 11 was heated in methanol, displacement ofchlorine from the heterocyclic ring gave the corresponding methoxyderivative (12) in 80% yield. Acid hydrolysis of 11 gave the 8-azaanalog (13a) of the carbocyclic xylofuranosylguanine 9a, whereastreatment of 11 with liquid ammonia gave the 8-aza analog (14a) of thecarbocyclic xylofuranosyl-2,6-diaminopurine 10a. Analogs 13b, 13c, and14b can be prepared as discussed above for analogs 9b, 9c, and 10b,respectively. Pharmaceutically-acceptable acid

salts of compounds 8-14 can be prepared as described in U.S. Pat. No.4,383,114.

The invention will be further described by reference to the followingdetailed examples, wherein elemental analyses were performed by M-H-WLaboratories, Phoenix, AZ. Melting points were determined on a Mel-Tempapparatus and are corrected. Nuclear Magnetic resonance (NMR) spectrawere obtained with a Joel FX 900 FT (89.55-MHZ), infrared spectra with aPerkin-Elmer 237B Spectrometer, and ultraviolet spectra with a BeckmanDU-8 recording spectrometer. Thin-layer chromatography (TLC) employed0.25 mm layers of Merck silica gel 60F-254 and column chromatographyused Merck silica gel (230-400 mesh). Mass spectra (MS) were obtainedwith an AEI Scientific Apparatus Limited MS-30 mass spectrometer.Low-resolution mass spectra were obtained for all compounds and themolecular ion and fragmentation patterns were reasonable for theassigned structures. Temperatures are given in °C. unless otherwisenoted.

EXAMPLE 1

(d1)-(1 α,2 β,3 α,5α)-3-[(2-Amino-6-chloro-4-pyrimidinyl)amino]-5-(hydroxymethyl)-1,2-cyclopentanediol(4).To 7.65 g (52.05 mmol) of (d1)-(1 α,2 β,3 α,5α)-3-amino-5-(hydroxymethyl)-1,2-cyclopentanediol (2) in 200 ml1-butanol and 25 ml methanol was added a mixture of 9.39 g (57.24 mmol)2-amino-4,6-dichloropyrimidine, 30 ml triethylamine and 50 ml 1-butanol.The resulting solution was refluxed for two days. The solvent wasevaporated in vacuo and the residue was partitioned between water anddichloromethane. The insoluble disubstituted product (5) was removed byfiltration to afford 5.90 g (39%) of an off-white solid. The aqueoussolution was washed with dichloromethane (3×30 ml) to remove unreacted2-amino-4,6-dichloropyrimidine and evaporated to dryness. The residuewas then evaporated onto coarse silica gel (70-230 mesh) which wassubsequently applied to the top of a flash chromatography (230-400 meshsilica gel) column. The column was eluted with acetone. Productfractions (Rf=0.31) were combined. The solvent was removed in vacuo toyield 4 as an off-white solid (4.84 g). An analytical sample wasrecrystallized twice from methanol/methylene chloride, mp 199°-200°; UV:εmax (λx 10⁻³) 271.4 (12.6), 240.6 (15.2) in 0.1 N HCl, 286.4 (10.1),238.1 (11.1), 211.4 (26.3) in H₂ O, and 286.4 (10.1), 238.9 (11.0),216.4 (16.6) in 0.1N NaOH; MS (70ev, 200°): m/e 274 (M⁺), 256 (M⁺ -H₂O), 243 (M⁺ -CH₂ OH), 225 (M⁺ -CH₂ OH-H₂ O), 171 (B+28), 145 (B+2H), 144(B+H), 143 (B), 128, 98, 67, 43; IR (KBr): 3500-3200 cm⁻¹ (NH, OH), 1660and 1595 (C=C, C=N); NMR (90 MHz, dimethylsulfoxide-d₆): δ 7.12 (br s,1H, NH), 6.40 (s, 2H, NH₂), 5.80 (s, 1H, Ar-H), 4.85-4.68 (2d, 2H,2CHOH), 4.55-4.20 (t, 1H, CH₂ OH), 3.62-3.12 (m, 5H, 2CHOH, CH₂ OH,CHN), 2.08-1.19 (m, 3H, CHCH₂ OH, CH₂); Anal. (C₁₀ H₁₅ N₄ O₃ Cl·1/2H₂ O)C, H, N, Cl.

An analytical sample of 5 was prepared by recrystallization fromethanol, mp 275°-276°; MS (20 ev, 200°): m/e 401 (M⁺), 370 (M⁺ -CH₂ OH),342 (M⁺ -59), 298 (B+28), 272 (B+2H), 271 (B+H), 270 (B); IR (KBr):3500-3200 cm⁻¹ (NH, OH), 1595, 1450, 1210, 980, 910, 815; NMR (90 MHz,dimethylsulfoxide-d₆); δ 9.82 (s, 1H, NH), 7.80-7.72 (br d, 1H, NH),7.54 and 6.16 (2s, 2H, 2Ar-H), 6.67 (s, 2H, NH₂), 5.05-4.69 (2d, 2H,2CHOH), 4.33-4.23 (t, 1H, CH₂ OH), 3.94-3.09 (m, 5H, 2CHOH, CH₂ OH,CHN), 2.15-1.33 (m, 3H, CHCH₂ OH, CH₂); Anal. (C₁₄ H₁₇ N₇ O₃ Cl₂.H₂ O)C, H, N, Cl.

EXAMPLE 2

(d1)-(1 α, 2 β, 3 α, 5α)-3-[[2-Amino-6-chloro-5[(4-chlorophenyl)-azo]-4-pyridiminyl]amino]-5-(hydroxymethyl)-1,2-cyclopentanediol(6). A cold (0°-5°) solution of p-chlorobenzenediazonium chloride wasprepared by adding a solution of 650 mg (9.50 mmol) sodium nitrite in 5ml water to a solution of 1.15 g (9 mmol) p-chloroaniline dissolved in 5ml of 12N HCl and 15 ml water and cooled in an ice-salt bath. The coldsolution of p-chlorobenzenediazonium chloride was added to a mixture of2.15 g (7.8 mmol) of 4, 17 g sodium acetate trihydrate, 40 ml aceticacid and 40 ml water at 25° C. The mixture as stirred for eighteen hoursat 25° C., then cooled in an ice bath. A yellow crystalline precipitate(6) was collected by filtration, washed with cold water, and dried:yield, 2.22 g (69%).

The product was recrystallized from methanol to yield 6 as a yellowpowder, mp 233°-236°; UV λ max in nm (ε×10⁻³) 372.2 (32.4), 280.6(11.3), 240.6 (24.6), 204.7 (21.9) in 0.1N HCl, 389.8 (41.6), 315.6(9.5), 280.6 (15.9), 219.8 (23.9) in MeOH, and 384.75 (16.3), 215.6(17.2) in 0.1N NaOH; MS (70 ev, 200): m/e 412 (M⁺), 286, 283 (B+2H), 281(B), 268, 238, 210, 182, 158, 146, 127, 114, 95, 65, 43; IR (KBr):3400-3100 (OH, NH), 1655, 1645, 1590, 1570 cm⁻¹ (Ar, C=C, C=N, NH); NMR(90 MHz, dimethylsulfoxide-d₆) δ 7.78-7.54 (m, 7H, Ar-H, NH₂, NH),5.06-5.02 (m, 2H, 2CHOH), 4.41-4.30 (t, 1H, CH₂ OH), 3.89-3.30 (m, 5H,CH₂ OH, 2CHOH, CHN) 2.31-1.22 (m, 3H, CHCH₂ OH, CH₂); Anal. (C₁₆ H₁₈ N₆O₃ Cl₂.H₂ O) C, H, N, Cl.

EXAMPLE 3

(d1)-(1 α, 2 β, 3 α, 5α)-[(2,5-Diamino-6-chloro-4-pyridiminyl)amino]-5-(hydroxymethyl)-1,2-cyclopentanediol(7). A solution of 2.00 g (4.84 mmol) of 6, 3.2 g zinc dust (200 mesh),1.6 ml acetic acid, 75 ml water and 75 ml ethanol was refluxed under anatmosphere of nitrogen. The reaction was followed by TLC and wascompleted within 1.5 hours. Excess zinc was removed by filtration, andthe solvent was evaporated to dryness. The brown residue was dissolvedin 50 ml water, and the aqueous solution was washed with methylenechloride to remove p-chloroaniline. After removal of water under reducedpressure, the residue was evaporated onto coarse silica gel, (70-230mesh) and applied to the top of a flash chromatography column (230-400mesh silica gel). The column was eluted with methylene chloride-methanol(4:1). The product fractions (Rf=0.28) were collected, combined, andevaporated to dryness and gave 759 mg (54%) of a pink solid.

Recrystallization from methanol-methylene chloride, and then from waterafforded 7 as a light pink solid, mp 187°-190°; UV: λmax (ε×10⁻³) 295.6(8.3), 238.9 (16.3), 210.6 (16.2) in 0.1N HCl, 303.1 (8.8), 204.8 (18.9)in H₂ O; and 303.1 (8.9), 224.8 (12.2) in 0.1N NaOH; MS (70 ev, 200°):m/e 289 (M⁺), 240 (B+14), 160 (B+2H), 15 g (B+H), 158 (B); IR (KBr):3500-3100 cm⁻¹ (NH, OH), 1635, 1605, 1510 (C=C, C=N, NH); NMR (90 MHz,dimethylsulfoxide-d₆): δ 6.46-6.38 (d, 1H, NH), 5.66 and 3.93 (2d, 4H,2NH₂), 4.82-4.69 (2d, 2H, 2CHOH), 4,31-4.19 (t, 1H, CH₂ OH), 3.72-3.32(m, 5H, 2CHOH, CH₂ OH, CHN), 2.17-1.35 (m, 3H, CHCH₂ OH, CH₂); Anal.(C₁₀ H₁₆ N₅ O₃ Cl) C, H, N, Cl.

EXAMPLE 4

(d1)-(1 α, 2 β, 3 α, 5α)-3-(2-Amino-6-chloro-9H-purin-9-yl)-5-(hydroxymethyl)-1,2-cyclopentanediol(8). A solution of 100 mg (0.345 mmol) of 7 and 3 ml drydimethylformamide was cooled to 0° and 5 ml of freshly distilledtriethylorthoformate and 0.1 ml of concentrated HCl were added. Theresulting mixture was stirred under nitrogen at 25° C. for 24 hours. Thesolvent was evaporated in vacuo to a dark red syrup. The syrup wasdissolved in 10 ml of 50% acetic acid and stirred at 25° C. for 4 hours.The solvent was then removed under reduced pressure and the residue wasstirred with methanolic ammonia (10% NH₃) at 25° C. for 4 hours. Thevolatile materials were removed in vacuo and the product was dissolvedin methanol-methylene chloride and refrigerated overnight. Thecrystallized product was removed by filtration to yield 52.9 mg (52%) of8 as a light pink solid.

An analytical sample was recrystallized from water to give 8 as anoff-white solid, mp 165°-167°; UV: λmax (ε×10⁻³) 313.1 (7.5), 243.1(6.2), 221.4 (25.6) in 0.1N HCl, 306.4 (7.4), 223.9 (25.9) in H₂ O; and307.2 (7.8), 249.8 (7.1), 223.9 (24.6) in 0.1N NaOH; MS (20 ev, 200°):m/e 299 (M⁺), 282 (M⁺ -OH), 268 (M⁺ -CH₂ OH), 250 (M⁺ -CH₂ OH-H₂ O), 196(B+28), 170 (B+2), 169 (B+1), 168 (B), 134, 81; IR (KBr): 3500-3000 cm⁻¹(NH₂, OH), 1635, 1560, 1465 (C=C, C=N); NMR (90 MHz dimethylsulfoxide-d₆): δ8.15 (s, 1H, Ar-H), 6.86 (s, 2H, NH₂), 5.36-5.05 (2d, 2H, 2CHOH),4.53-4.38 (t, 1H, CH₂ OH), 4.17-3.11 (m, 5H, 2CHOH, CH₂ OH, CHN),2.26-1.70 (m, 3H, CHCH₂ OH, CH₂); Anal. (C₁₁ H₁₄ N₅ O₃ Cl) C, H, N, Cl.

EXAMPLE 5

(d1)-2-Amino-1,9-dihydro-9-[(1 α,2 β,3 α,4α)-2,3-dihydroxy-4-(hydroxymethyl)cyclopentyl]-6H-purin-6-one (9a). Asolution of 100 mg (0.345 mmol) of 7 and 3 ml dry dimethylformamide wascooled to 0° C. and 5 ml of freshly distilled triethylorthoformate and0.1 ml conc. HCl were added. The reaction mixture was stirred undernitrogen at room temperature for 24 hours. The solvent was evaporatedand the residue was dissolved in 10 ml of 1N HCl. The solution wasrefluxed for 5 hours and then the water was evaporated and azeotropedwith absolute ethanol. The liquid residue was dissolved in a smallamount of water and the solution was neutralized to pH 6 with 1N NaOH. Awhite precipitate formed immediately and the suspension wasrefrigerated. The solid product was collected by filtration and washedwith cold water to yield 63.2 mg of 9a (65%) as an off-white powder, mp254°-256°.

An analytical sample was recrystallized from water, mp 291°-293°; UV:λmax (ε×10⁻³) 255.6 (12.4), 202.2 (41.75) in 0.1N HCl, 253.1 (14.7),189.8 (31.7) in H₂ O, and 268.1 (12.4), 217.2 (18.9) in 0.1N NaOH; MS(70 ev, 200°): m/e 281 (M⁺), 264 (M⁺ -OH), 178 (B+28), 152 (B+2H), 128,98, 81, 67, 43; IR (KBr): 3400-3150 cm⁻¹ (NH, OH), 1725 (C=O), 1640,1550, 1490 (C=C, C=N, NH); NMR (90 MHz, dimethylsulfoxide-d₆): δ 10.54(s, 1H, NH), 7.71 (s, 1H, Ar-H), 6.39 (s, 2H, NH₂), 5.32-5.04 (2d, 2H,2CHOH), 4.41- 4.30 (t, 1H, CH₂ OH), 4.24-3.32 (m, 5H, 2CHOH, CH₂ OH,CHN), 2.28-1.38 (m, 3H, CHCH₂ OH, CH₂); Anal. (C₁₁ H₁₅ N₅ O₄.11/2H₂ O)C, H, N.

EXAMPLE 6

(d1)-1 α,2 β,3 α,5α)-3-(2,6-Diamino-9H-purin-9-yl)-5-(hydroxymethyl)-1,2-cyclopentanediol(10a). A solution of 61.2 mg (0.204 mmol) of the chloro compound, 8, in2 ml methanol was transferred into a stainless steel bomb and themethanol was evaporated by a stream of nitrogen. Excess ammonia wasadded and the sealed bomb was heated at 80° for 2 days. Evaporation ofthe ammonia left a yellow residue which was dissolved in 5 ml of hotwater. Refrigeration of the solution yielded 41.0 mg (72%) of paleyellow semisolid. Recrystallization from water afforded 10a as a paleyellow powder, mp 234°-237°; UV: λ max (ε×10⁻³) 291.4 (9.7), 253.1(9.5), 218.9 (20.8) in 0.1N HCl; 279.8 (10.5), 255.6 (8.6), 215.6 (28.1)in H₂ O; and 280.6 (10.2), 255.6 (8.1), 218.9 (22.5) in 0.1N NaOH; MS(70 ev, 200°): m/e 280 (M⁺), 263 (M⁺ -OH), 249 (M⁺ -CH₂ OH), 231 (M⁺-CH₂ OH-H₂ O), 177 (B+28), 163 (B+14), 151 (B+2), 150 (B+1), 149 (B),134, 108, 57, 43, 28; IR (KBr): 3600-3100 cm⁻¹ (OH, NH₂), 1665, 1600,1495 (C=C, C=N, NH); NMR (90 MHz, dimethylsulfoxide-d₆): δ 7.73 (s, 1H,Ar-H), 6.69 (s, 2H, NH₂), 6.61 (s, 2H, NH₂), 5.86-5.77 (m, 2H, 2CHOH),4.36-3.67 (m, 6H, CHN, CH₂ OH, 2CHOH, CH₂ OH), 2.21-1.82 (m, 3H, CHCH₂OH, CH₂); Anal. (C₁₁ H₁₆ N₆ O₃) C, H, N.

EXAMPLE 7

(d1)-(1 α,2 β,3 α,5 α)-3-(5-Amino-7-Chloro-3H-1,2,3-triazalo[4,5-d]pyrimidin-3-yl)-5-(hydroxymethyl)-1,2-cyclopentanediol (11). Asolution of 26.0 mg (0.380 mmol) of sodium nitrite in 1 ml water wasdrop-wise added to a 0° C. solution of 100 mg (0.345 mmol) of 7 in 1 mlwater and 0.5 ml of glacial acetic acid. The solution was stirred at 0°for 2 hours and at 25° C. for 1 hour. The solvent was removed in vacuo(below 20°) and the residue was evaporated onto silica gel and thenapplied to the top of a flash chromatography column. The column waseluted with methylene chloride-methanol (4:1). The product fractionswere collected (Rf=0.53), combined, and concentrated in vacuo to obtain73.0 mg (70%) colorless solid, mp softens at 130°-150° and melts at220°-230°.

An analytical sample of 11 was obtained by recrystallization frommethanol, mp softens at 121° and melts at 220°-223°; UV: λmax (ε×10⁻³)314.8 (8.6), 225.6 (24.1) in 0.1N HCl; 314.8 (8.2), 225.6 (24.4) in H₂O, and 222.2 (24.3) in 0.1N NaOH; MS (20 ev, 250°): m/e 283 (M⁺ -OH),171 (B+2H), 170 (B+H), 169 (B), 144, 112, 84, 69; IR (KBr): 3600-3250cm⁻¹ (OH, NH₂), 1650, 1610, 1470 (C=C, C=N, NH); NMR (90 MHz,dimethylsulfoxide-d₆): δ 7.60 (s, 2H, NH₂), 5.35-5.29 (d, 1H, CHOH),5.00-4.95 (d, 1H, CHOH), 4.62-3.60 (m, 6H, CHN, CH₂ OH, CH₂ OH, 2CHOH),2.23-2.15 (m, 3H, CHCH₂ OH, CH₂); Anal. (C₁₀ H₁₃ N₆ O₃ Cl.H₂ O) C, H, N,Cl.

EXAMPLE 8

(d1)-(1 α,2 β,3 α,5 α)-3-(5-Amino-7-methoxy-3H-1,2,3-triazalo[4,5-d]pyrimidin-3-yl)-5-(hydroxymethyl)-1,2-cyclopentanediol (12). Asolution of 54.1 mg (0.179 mmol) of 11 in methanol was refluxed for 1hour. The solvent was evaporated to dryness to obtain 42 mg (80%) of 12as a colorless semisolid. Crystallization from methanol gave 28.2 mg of12 (53%) as a pure solid product, mp 157°-159°; UV: λmax (ε×10⁻³) 282.2(10.7), 213.9 (23.6) in 0.1N HCl, 287.2 (9.7), 216.4 (23.4) in H₂ O; and285.6 (10.6), 218.9 (22.9) in 0.1N NaOH; MS (30 ev, 220°): 296 (M⁺),283, 247 (M⁺ -CH₂ OH-H₂ O), 223, 209, 181, 167 (B+2H), 166 (B+H), 165(B), 139, 110, 96, 83, 67, 53, 43; IR (KBr): 3500-3200 cm⁻¹ (NH₂, OH)1665, 1610, 1465 (C=C, C=N, NH); NMR (90 MHz, dimethylsulfoxide-d₆): δ7.07 (s, 2H, NH₂), 5.34-5.28 (d, 1H, CHOH), 4.99-4.93 (d, 1H, CHOH),4.58-3.51 (m, 6H, CHN, CH₂ OH, CH₂ OH, 2CHOH), 4.05 (s, 3H, OCH₃),2.47-1.55 (m, 3H, CHCH₂ OH, CH₂); Anal. (C₁₀ H₁₃ N₆ O₃ Cl.H₂ O) C, H, N.

A similar procedure can be employed to replace the chloro substituent of8 with (lower)alkoxy substituents.

EXAMPLE 9

(d1)-5-Amino-3,6-dihydro-3-[(1 α,2 β,3 α,5α)-2,3-dihydroxy-4-(hydroxymethyl)cyclopentyl]-7H-1,2,3-triazalo[4,5-d]pyrimidin-7-one(13a). A solution of 91.3 mg (0.304 mmol) of 11 in 10 ml 1N HCl wasrefluxed for 5 hours. The solvent was removed in vacuo and the resultingyellow solid was crystallized from water and afforded 47.0 mg (55%) ofpale yellow powder; mp 235°-238° dec.

A second recrystallization from water gave pure 13a as pale yellowcrystalline solid, mp 241°-244° dec.; UV: λ max (ε×10⁻³) 253.9 (12.3),207.2 (20.8) in 0.1N HCl, 253.1 (12.4), 203.1 (23.1) in H₂ O; and 278.9(11.6), 220.6 (25.6) in 0.1N NaOH; MS (20 ev, 200°): m/e 187, 167, 153(B+2H), 134, 121, 107, 84, 70; IR (KBr): 3600-3200 cm⁻¹ (NH₂, OH), 1710(C=O), 1600, 1530 (C=C, C=N), NMR (90 MHz dimethylsulfoxide-d₆): δ 11.20(s, 1H, NH), 7.18 (s, 2H, NH₂), 5.37-5.63 (d, 1H, CHOH), 5.02-4.96 (d,1H, CHOH), 4.41-3.32 (m, 6H, CHN, CH₂ OH , CH₂ OH, 2CHOH), 2.28-2.01 (m,3H, CHCH₂ OH, CH₂); Anal. (C₁₀ H₁₄ N₆ O₄.3/4H₂ O) C, H, N.

EXAMPLE 10

(d1)-(1 α,2 β,3 α,5α)-3-(5,7-Diamino-3H-1,2,3-triazalo[4,5-d]pyrimidin-3-yl)-5-(hydroxymethyl)-1,2-cyclopentanediol(14a). A mixture of 94.1 mg (0.313 mmol) of 11 in liquid ammonia washeated in a stainless steel bomb at 80° for 48 hours. Evaporation ofammonia left a solid residue which was crystallized from water andafforded 47.2 mg (54%) pale yellow solid, mp 219°-224°.Recrystallization from water afforded pure 14a as a pale yellow powder,mp 231°-233°; UV: -λmax (ε×10⁻³) 286.4 (8.1), 256.4 (10.1), 213.9 (26.6)in 0.1N HCl; 287.2 (11.3), 260.6 (6.4), 223.9 (27.2) in H₂ O; and 286.4(11.6), 260.6 (6.8), 223.9 (28.5) in 0.1N NaOH; MS (30 ev, 330°): m/e281 (M⁺), 232, 194, 163, 152 (B+2H), 150 (B), 126, 113, 110, 43; IR(KBr): 3600-3250 cm⁻¹ (OH, NH₂), 1610, 1645, 1460 (C=C, C=N, NH); NMR(90 Mhz, dimethylsulfoxide-d₆): δ7.53 (s, 2H, NH₂), 6.34 (s, 2H, NH₂),5.37-5.31 (d, 1H, CHOH), 5.06-5.00 (d, 1H, CHOH), 4.55-3.52 (m, 6H, CHN,CH₂ OH), CH₂ OH, 2CHOH), 2.26-2.05 (m, 3H, CHCH₂ OH, CH₂); Anal. (C₁₀H₁₅ N₇ O₃.1/4H₂ O) C, H, N.

EXAMPLE 11

(d1)-(1 α,2 β,3 α,5α)-3-(2-Amino-6-mercapto-9H-purin-9-yl)-5-(hydroxymethyl)-1,2-cyclopentanediol(9b). A solution of 1.09 mmol of 8 and 1.86 mmol of thiourea in1-propanol (8 ml) is refluxed for 0.75 hour. The reaction mixture iscooled and the precipitate isolated by filtration and washed with1-propanol. The isothiourea hydrochloride powder is refluxed for 2 hourswith aqueous sodium hydroxide according to the procedure of G. G.Urquhart et al., Org. Syn. Coll. Vol., 3, 363 (1955) to yield 9b. Asimilar procedure is used to prepare 13b from 11.

EXAMPLE 12

(1 α,2 β,3 α,5α)-d1-3-(2-Amino-6-methylthio-9H-purin-9-yl)-5-hydroxymethyl)-1,2-cyclopentanediol(9c, R'=CH₃). A mixture of crude 9b (0.62 mmol), methyl iodide (0.25ml), 1.0N NaOH (0.62 ml) and 2.0 ml water is stirred at 25° C. for 4hours. The resulting solution is evaporated to dryness and the residuechromatographed on a column of silica gel G (Brinkman, 20 g, packed inCHCl₃). Elution with methanol-CHCl₃ affords 9c, R'=CH₃.

Cytotoxicity Assay

The ED₅₀ cytotoxicity concentrations determined for analogs 8, 9a, 10a,11, 12, 13a and 14a in the P-388 mouse leukemia cell culture assay aregiven in Table I. Carbocyclic nucleosides 9a, 13a, and 14a exhibitedsignificant cytotoxicities in this assay. The 8-aza guanine and purineanalogs 13a and 14a are more active than the corresponding guanine andpurine analogs, 9a and 10a.

                  TABLE I                                                         ______________________________________                                        Inhibitory Concentrations of Carbocyclic Xylofuranosides of                   2-Amino-6-substituted-purines and 2-Amino-6-substituted-8-                    azapurines for P-388 Leukemia Cells in Cultures.*                             Compound      ED.sub.50, μM                                                ______________________________________                                        8             220.0                                                            9a           8.9                                                             10a           39.0                                                            11            50.0                                                            12            63.0                                                            13a           1.6                                                             14a           5.3                                                             ______________________________________                                         *Assay Technique: R. G. Almquist and R. Vince, J. Med. Chem., 16, 1396        (1973).                                                                  

Antiviral Assay

Analogs 9a, 10a, 13a, and 14a were evaluated for in vitro antiviralactivity against HSV-1. Analogs 9a and 13a were further evaluated foractivity against HSV-2. The analogs were evalulated by a cytopathogeniceffects (CPE)-inhibition procedure. The host cell culture systemsemployed were pre-grown Vero cell monolayers. The results of theseassays are summarized in Table II, below. A virus rating of one orgreater is indicative of a compound with a favorable balance between itsantiviral effect and its cytotoxicity to the host cells.

                  TABLE II                                                        ______________________________________                                        Compound     HSV-1 (E-377) HSV-2 (MS)                                         No.          VR*    MIC.sub.50 **                                                                            VR*  MIC.sub.50 *                              ______________________________________                                         9a          5.6     3.0       3.9  23.5                                      10a          2.7    85.0       --   --                                        13a          2.4    60.8       1.3  92.2                                      14a          2.0    66.9       --   --                                        Positive Control:                                                                          1.7    21.8       1.6  40.6                                      Ara-A                                                                         ______________________________________                                         *VR = virus rating: A measurement of selective antiviral activity which       takes into account the degree of inhibition of virusinduced cytopathogeni     effects (CPE) and the degree of cytotoxicity produced by the test             compound, determined by a modification of the method of Ehrlich et al.        (Ann. N.Y. Acad. Sci. 130: 5-16, 1965). A VR ≧ 1.0 indicates           definite (+) antiviral activity, a VR of 0.5-0.9 indicates marginal to        moderate (+) antiviral activity, and a VR < 0.5 usually indicates no (-)      significant antiviral activity.                                               **MIC.sub.50 = Minimum inhibitory concentration required for 50%              inhibition of virusinduced CPE (in μg/ml).                            

The data presented in Table II demonstrate that analogs 9a, 10a, 13a and14a exhibit substantial antiviral activity against HSV-1, while 9a and13a are also active against HSV-2 ("genital herpes"). However, while the2-amino-8-aza-guanine analog 13a exhibited inhibition at the lowestconcentration in the cytotoxicity assay, 2-aminoguanine analog 9aexhibited the best profile of activity in the antiviral assay. Of theanalogs listed in Table II, only 13a exhibited any significant activityagainst an influenza virus.

The invention comprises the biologically-active xylofuranosyl purines asdisclosed or the pharmaceutically acceptable salts or esters thereof,together with a pharmaceutically acceptable carrier for administrationin effective non-toxic dose form. Pharmaceutically acceptable salts maybe salts of organic acids, such as acetic, lactic, malic, or p-toluenesulphonic acid, and the like as well as salts of pharmaceuticallyacceptable mineral acids, such as hydrochloric or sulfuric acid, and thelike. Other salts may be prepared and then converted by conventionaldouble decomposition methods into pharmaceutically acceptable saltsdirectly suitable for purposes of treatment of viral infections inmammals or for the prevention of viral contamination of physiologicalfluids such as blood or semen in vitro.

Pharmaceutically acceptable carriers are materials useful for thepurpose of administering the present analogs and may be solid, liquid orgaseous materials, which are otherwise inert and medically acceptableand are compatible with the active ingredients. Thus, the present activecompounds can be combined with the carrier and added to physiologicalfluids in vitro or administered in vivo parenterally, orally, used as asuppository or pessary, applied topically as an ointment, cream,aerosol, powder, or given as eye or nose drops, etc., depending uponwhether the preparation is used for treatment of internal or externalviral infections.

For internal virus infections, the compositions may be administeredorally or parenterally at effective non-toxic antivirus dose levels ofabout 50 to 750 mg/kg/day of body weight given in one dose or severalsmaller doses throughout the day. For oral administration, fine powdersor granules may contain diluting, dispersing and/or surface activeagents and may be presented in water or in a syrup; in capsules in thedry state, or in a non-aqueous solution or suspension; in tablets, orthe like. Where desirable or necessary, flavoring, preserving,suspending, thickening or emulsifying agents may be included. Forparenteral administration or for administration as drops, as for eyeinfections, the compounds may be presented in aqueous solution in aneffective nontoxic dose in concentration of from about 0.1 to 10 percentw/v. The solutions may contain antoxidants, buffers, and the like.Alternatively, for infections of the eye or other external tissues, thecompositions are preferably applied as a topical ointment or cream inconcentration of about 0.1 to 10 percent w/v.

It is apparent that many modifications and variations of this inventionmay be made without departing from the spirit and scope thereof. Thespecific embodiments described are given by way of example only and theinvention is limited only by the terms of the appended claims.

What is claimed is:
 1. A method for protecting mammalian cell againstinfection by a virus comprising bringing said cells into contact with aneffective amount of the compound in a pharmaceutically-acceptablecarrier.
 2. The method of claim 1 wherein said virus is HSV-1 or HSV-2.3. A compound of the formula: ##STR6## wherein X is CH and R is selectedfrom the group consisting of N(Y)(Z), SY, OY and halogen, wherein Y andZ are H, lower(alkyl) or phenyl; and the pharmaceutically-acceptablesalts thereof.
 4. The compound of claim 3 wherein R is chloro.
 5. Thecompound of claim 3 wherein R is NH₂ or OH.
 6. The compound of claim 5wherein R is NH₂.
 7. The compound of claim 5 wherein R is OH.
 8. Acompound of the formula: ##STR7## wherein X is N and R is selected fromthe group consisting of N(Y)(Z), SY, OY and halogen, wherein Y and Z areH, lower(alkyl), phenyl or mixtures thereof; and thepharmaceutically-acceptable salts thereof.
 9. The compound of claim 8wherein R is chloro.
 10. The compound of claim 8 wherein R is NH₂ or OH.11. The compound of claim 10 wherein R is NH₂.
 12. The compound of claim10 wherein R is OH.